Circuit for multi-aperture magentic core devices



Oct. 24, 1967 p. NITZAN CIRCUIT FOR MULTI-APERTURE MAGNETIC CORE DEVICES n N d 1 no m a 8 m L o 3 N T e I z 0 El h a S N C t 2 w w 2 2 D Y H o o W 2 N m m A Aw m D m Du w w 0 w p. a I I 8 T 6 5 4- a 2 O m w 6 2 Nrr o w u w ME: z U C B 0 N rr rm r m N: U w o o o n e m a 3l F Jn d 1 W .%o o Aw flFWM I 0. L W 3 .N o W o A m w I. v II I .I v M h H d l. a Pbt h I 6 n 4 5 Z O. F. A a m MMNNN V Oct. 24, 196-7 D. NITZAN 3,349,330

I CIRCUIT FOR MULTI-APERTURE MAGNETIC CORE DEVICES Filed Aug. 50, 1963 2 Sheets-Sheet 2 I 6 u :6 =3 "i=3 N:5 I N :3 Li u N S X46 w NQGrm 0 -4o 30 no 160200 240 230 320 Ip z c. N! NX=3 ,5 u =6 NW3 2 ,NHzo

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- JDAVsD NITZAN BY United States Patent 3,349,380 CIRCUIT FOR MUL'I'I-APERTURE, MAGNETIC CORE DEVICES David Nitzan, Palo Alto, Calif., assignor to AMP Incorporated, Harrisburg, Pa. Filed Aug. 30, 1963, Ser. No. 305,779 9 Claims. (Cl. 340-174) This invention relates to an improved circuit and method for multi-aperture magnetic core devices of the type utilized to manipulate intelligence in binary form.

One of the more successful techniques developed relative to the use of multi-aperture cores for handling intelligence, is that generally shown and described in the article, MAD-Resistance Type Magnetic Shift Registers, by Dr. David R. Bennion, 1960 ProceedingsAIEE, Special Technical Conference on non-linear Magnetics and Magnetic Amplifiers, Philadelphia Conference, Oct. 26- 28, 1960. A specialized variation of the MAD-R technique described by Dr. Bennion, has been developed for applications wherein the advance drive pulses for two or more core devices must be asynchronous. An example of this circuit is shown in US. patent application, Ser. No. 50,695, now abandoned, filed Aug. 19, 1960, by John C. Mallinson, a continuation of which issued as US. Patent No. 3,178,694. While application experience has uncovered more and more uses for the transfer loop-core coupling described in the Mallinson application, it has at the same time indicated certain operational deficiencies with respect to total range of operation of the unit in the presence of expected temperature and drive supply variation.

More particularly, the specialized variation above mentioned includes a feature wherein the coupling loop which operates to transfer intelligence from core to core, links the outer leg of a minor aperture of one core and the inner leg of the same relative minor aperture of a succeeding core. This feature may be termed Leg 4 to Leg 3 transfer referencing the outer and inner legs of each minor aperture. While certain embodiments of the specialized variation, as for example devices made in accordance with the above mentioned Mallinson application, have proven satisfactory in operation, such devices fall far below, in total limits of operation, standard MAD-R circuits, having transfer loops coupling a succeeding core major path or a receiving minor aperture of such core. In a word, the specialized variations under consideration are being used, but, because of limited range of operation are recognized as the weak link in MAD-R systems.

Accordingly, it is an object of the present invention to provide a MAD-R device having transfer loops coupling the outer leg of the transmitting aperture of one core to the inner leg of the transmitting aperture of a succeeding core in conjunction with an improved circuit extending the range of operation of the device.

It is a further object of the invention to provide a MAD-R device having a Leg 4 to Leg 3 transfer loop with circuit and drive improvements extending the range of operation of the device to be compatible with other MAD- R circuits.

It is another object of invention to provide an improved MAD-R device and method for controlling the characteristics of the operational range thereof.

Other objects and attainments of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings in which there is shown and described illustrative embodiments of the invention; it is to be understood, however, that these embodiments are not intended to be exhaustive nor limiting of the invention, but are given for purpose of illustration in order that others skilled in the art may fully understand the invention and the principles thereof and the manner of applying it in practical use so that they may modify it in various forms, each as may be best suited to the conditions of a particular use.

The foregoing objects are attained in the present invention through the addition of windings which operate to provide magnetomotive forces sutficient and properly phased to prevent backward transfer from a given transmitting core to a receiving core during the transmission phase of the given core. The circuit of the invention in corporates such windings without additional supply requirements by having the added turns supplied by existing advance circuits. Additionally the invention contemplates use of different drive turns ratios with different types of prime drive current to achieve desired control over the operational range characteristics of the circuit of the invention.

In the drawings:

FIGURE 1 is a schematic diagram of a portion of a series of magnetic cores with the circuit of the invention incorporated in a shift register circuit;

FIGURE 1a is a schedule of the function and identity of winding turns N for the circuit of FIGURE 1;

FIGURE 2 is a range map for the device of FIGURE 1;

FIGURE 3 is a range map showing the operation of prior art devices; and

FIGURES 4 and 5 depict range maps showing the re lationship of Winding turns ratios to range of operation.

Referring first to FIGURE 3, there is shown a range map representative of the range of operation of prior art devices, as for example, the shift register device shown in the above mentioned patent to Mallinson. With respect to MAD-R devices, this type of range map has come to be accepted as the basic and standard gauge of unit operation with the shape and spread of the curve shown therein being determinative of success or failure. The abscissa and ordinate of FIGURE 3 represent values of prime and advance currents I and I in milliamperes and amperes, respectively. The area defined by the curve in FIGURE 3 corresponds to a region of bistable operation, i.e., where ones and zeros are sustained faithfully in a closed-loop shift register.

Consider, for example, that a given MAD-R unit is supplied with I and I values to operate at point 0P as shown in FIGURE 3. At this point, and at any point within the curve shown, binary intelligence in the form of one or zero will be retained or transferred between cores in the unit without alteration. As one of the hard facts of commercial use of magnetics, components of the driver circuits supplying I or 1;. change their operating parameters in the presence of time, heat and the like. Additionally, voltage supplies to the I and I driver circuits vary substantially, resulting in variations in I and I from a given initial point of operation to points such as 0P 0P and 0P This is particularly true wherein I is supplied by a DC. source or by a pulse source phased to overlap, in time, the I pulses. Finally, the magnetic unit itself will exhibit changes in operation determined by the temperature coefiicients of the magnetic material and the copper wireemployed in the unit. These changes manifest themselves by shifting the ambient curve T of FIGURE 3, downwardly and to the left with increases in temperature and upwardly and to the right with decreases in temperature, as indicated by curve positions T and T respectively. There is also a change in range size, usually to a smaller area at T and a larger area at T Consider, for example, increases in I and in 1;. caused solely by supply voltage variations which, in combination, result in the device operating point becoming 0P A device experiencing elevated temperatures and operating with range T will operate improperly, spuriously losing intelligence. Consider the same case with no change in I and a substantial increase in I to produce an operating point P in conjunction with an increase in temperature shifting the range to T This would also cause spurious operation of the magnetic unit. Similarly, a decrease in temperature to the range position T combined with slight changes in I and I will result in an operation point OR; and malfunction of the unit. In digital devices as distinguished from analog devices, all expected variations and operational tolerances must be arranged so as to preclude the loss of even a single bit of intelligence.

If a given MAD-R device has a range as depicted in FIGURE 3, compensation or expensive extra steps must be taken when the device is to be utilized in conjunction with other MAD-R units or other electronic units which must meet military and civilian specifications. For example, special high cost voltage supplies and high cost driver circuits must be employed to limit variations of the operating point outside of the curve of the range of operation. Additionally, in critical applications, special environment controls and isolation procedures must be employed to prevent the magnetic core material and copper conductors from being exposed to changes in temperature resulting in transposed ranges of operation. The meaning of this is that MAD-R circuits having ranges as shown in FIGURE 3, are basically incompatible with other MAD-R units with respect to total range of operation.

Referring now to FIGURES 1 and 2, there is shown the improved circuit of the invention and its range of operation for certain drive turns ratios and prime current applied. The range map shown in FIGURE 2 is substantially identical to the design range map of standard MAD-R units. As indicated in FIGURE 2, variations in I and I and variations in temperature may be quite substantial without resulting in any of the operating points OP OP being outside of the overlap between the positions of the range maps for ambient, elevated and reduced temperatures.

In FIGURE 1, three multi-aperture cores are shown and represent the 0 E 0 cores of a unilateral shift register employing Leg 4' to Leg 3 transfer loops.

Each of the cores 10 is comprised of a hard-fired ferrite magnetic material having a substantially square hysteresis loop exhibiting a defined bistability to accommodate the storage of distinct intelligence states in binary form. The particular geometry shown to represent cores 10 in FIG- URE l, is that of a standard four minor aperture core manufactured by the Indiana General Corporation of Valparaiso, Ind., and identified as their material No. 5209. The core is generally symmetrical and includes a central major aperture 12, with four symmetrically disposed minor apertures 14 of substantially the same diameter. The core is eared adjacent the exterior of each aperture such that the cross-sectional area, through any section of the core, is substantially the same with the cross-sectional area being substantially equal in each half of the section through a minor aperture. In each core 10 the legs denominated L and L represent receiving and transmitting core legs, respectively.

While single core structures are shown, it is fully contemplated that the invention may be adapted to composite core structures defined by a single slab of ferrite or even other magnetic material exhibiting similar characteristics and including individual bit positions which simulate individual cores.

The circuit shown in FIGURE 1, is driven in the usual MAD-R cycle as explained in the article by Dr. Bennion, to advance intelligence from O to E to 0 cores responsive to the application of Advance 0, Prime E, Advance E, Prime 0, phases in sequence. The various leads shown forming the advance, prime and transfer leads are Formvar insulated solid copper conductors connected in the polarities indicated in FIGURE 1. The particular turns N shown and identified in FIGURE 1a are related to the currents employed such that a particular NI (or Ni) is sufficient to perform the function required. As will be 4 demonstrated hereinafter, the ratios of various turns N as well as the characteristics of I may be varied to obtain control over the unit range.

Considering now the operation of the circuit in FIG- URE 1 with respect to operational sequence, with all of the cores 10 in the zero state conventionally represented by a closed flux path circulating in the clockwise sense (the cores being in negative saturation), the application of a one input to core 0 via coupling winding 24 and turns N will reverse the orientation of flux in the inner leg surrounding aperture 12, such that the core is then set (the core being half in a state of half negative, half positive saturation). .The one input may be considered as a current pulse developed from any suitable source or from a core preceding 0 The intelligence states of the three cores 10 will then be one-zero-zero and the normal transfer cycle will result in a prime current I being applied to lead 22 to effect a localized reversal of flux in legs L and L, of 0 the MMFs N I and NJ acting together to assure that L is fully positively saturated and that the demagnetized state of the core major path is not disturbed. Cores E and 0 will not of course, be disturbed since the amplitude of I is held less than the threshold of a core in the soft or set state and therefore considerably less than the threshold of a core in the clear state. The application of I via lead 18 will then operate through turns N and N to drive core 0 into the clear state producing a d/dt resulting in a current i; in loop 26 coupling L As with standard MAD-R, N i will set core E the content of the cores 10 then being zero-onezero. The application of I to winding 22 will then prime core E in the manner above described and the application of I on lead 20 will clear core E and transfer the one to core 0 to provide an information content of zero-zero-one.

Further application of I and I will advance the information in register to a content of zero-zero-zero. The operation thus far described is similar to that of prior art devices and might be expected to provide a range map as shown in FIGURE 3. The circuit and method of the present invention, which prevents such is in part, based upon discoveries related to the use hold turns N added to the transmitting aperture of a core and to the characteristics of prime current applied. Before developing this fully, the role of N, with respect to operational sequence should be in mind.

As a basic point relating to the addition of hold turns N to the circuit is the concomitant incorporation of N into the advance circuits such that the ADV. 0 lead 18 includes N turns linking core E and the ADV. E lead 20 includes N turns linking cores O and 0 This feature assures that the MMF, N I will be properly phased with respect to its purpose in holding a preceding core against being set by back currents developed in a succeeding set core being cleared by I Additionally, since I in amplitude and rise time, is partly responsible for the back-current problem, the use of I to provide holding MMF is more than merely convenient.

Referring back to the zero-one-zero state of information in register above described, the application of 1;. followed by I on lead 20 operates to clear core E through turns N and N to develop i in winding 28 and set 0 as above described. The application of I on lead 20 also provides an MMF, N I operating on the L legs of core 0 and O simultaneously in a sense to hold the legs L; in the clear or clockwise sense. With regard to core 0 the holding of L will not prevent the core from being set since it is the inner path including L which is switched to the counter-clockwise state to define a one input. With respect to core 0 the application of MI; in holding L serves to prevent flux from being switched by the back current i flowing in transfer loop 26 and developed by flux switched in L of E It is to be noted that the sense of i is such as to tend to set flux in core 0 and while the quantity of flux which would be set will be substantially less than necessary for a complete one set,

it can operate to disturb the full clear state. This has been found to have an adverse effect upon the zero level transfer produced when core 0 is cleared. Thus, for example, if only 20 percent of the core material were set by i the discrimination between one and Zero transfer would be reduced from six to one down to two to one; the combination of elastic flux and flux set by i operating to so boost the zero flux switched. If this additional quantity of flux is generated in each transfer, a false one will be generated within a single advance cycle. Thus, without N in the sequence above given the intelligence content would be an erroneous one-zero-one following the application of ADV. E rather than zero-zero-one.

In View of the prior art treatment of the explanation of L -L transfer, it might be expected that i would be so insubstantial as to have no effect. See for example, the flux arrow diagram in the aforementioned Mallinson case, wherein during advance time leg L appears to be uneifected remaining with the clockwise flux orientation existent before and after the application of ADV. E. In fact, because of this reasoning the relatively poor range map achieved by the prior art, L and L MAD-R transfer was not fully understood. Actual measurements of i however, led to the conclusion that with either N or N and N clearing, a very substantial i is developed in the coupling loop linking a preceding nontransmitting core to a transmitting core; i being-higher with N I clearing than with N I and N I clearing. One reason was found to be due to excess material in L adjacent the transmitting minor aperture. Other test evidence led to the conclusion that the i developed was due to the'M-MF caused by i in steering flux into the leg L which has the effect of switching elastic flux if L is properly cleared and both elastic and elastic flux if L is improperly primed in the clear sense. This led to a realization of the role of N in increasing flux gain; since N I not only decreases dzp/dt in L but also increases d/dt in L to produce a higher i The net effect of N I is to raise the top boundary when N =0 by decreasing i and lower the bottom boundary by increasing if. Extreme values of I may cause zero build up.

Viewing now FIGURES 4 and 5, the role of N with respect to other turns N and N and with respect to the characteristics of prime drive will be reviewed. In both figures the range map wherein N is not zero, represent the circuit of the invention shown in FIGURE 1. In both figures the range map wherein N equals zero, represents the range map of the prior device shown for comparison.

Turning first to FIGURE 4, the DC. prime case, the circuit of FIGURE 1 may be considered as supplied by a source of DC. current which is on continuously during the various advance-prime phases. It will be appreciated that the use of DC. prime considerably simplifies the drive requirements for the circuits since no separate pulse developing means need be utilized and there is no synchronizing problem. For this reason, the use of DC. prime is attractive in applications wherein cost is more important than total range of operation. Even so, there are certain minimum range requirements. The range map indicated in FIGURE 4 for N =0 is below these minimum requirements in that there is virtually no range in the area of higher values of I and I By making N =3 in conjunction with N =3 and N =3, we see a very substantial improvement in the total area of proper operation with the right-hand boundary being opened up and extended vertically, the top boundary being extended and the bottom boundary being somewhat higher. While the loss of some of the range for lower values of I is undesirable, it can be tolerated in certain applications when the remainder of the range is sufiiciently large to permit substantial deviations of I and particularly when the range permits substantial deviations I as it does in the N =N =N =3 cases. The reason for the reduction in the bottom boundary with N =0 is due to higher gain with respect to forward transfer, wherein the MMF developed by i is not opposed by N I Turning now to FIGURE 5, I is, as indicated, nonoverlapping prime. This means that I is developed by current pulses, which begin in time after the application of I The range maps shown were made with I with a duration of 80 microseconds. As indicated, by making N =3, N=3 and N =3, a very substantial improvement in the range is achieved whereby both the right and left boundaries are opened up and the top boundary is considerably extended. The lower boundary is very slightly reduced, but the area of the range of proper operation is more than doubled with considerable linearity of boundary to provide good overlap in the presence of temperature changes as explained with respect to FIGURE 2. The addition of more N turns such that N =6 with N =3 and N 3, further extends the top boundary with a slight depreciation in lower boundary and a slight improvement in right boundary. The improvement appears to hold even where I pulses begin before I pulses have ceased.

It has been found that by reducing the time of application of I to approximately 40 microseconds the lower boundary in both the above curves with N =3 there is substantial improvement in the lower boundary. It has been also found that a circuit including N =6 N and N -=1, will provide adequate operation with ranges somewhat reduced from those indicated, but nevertheless,

far superior to the Nh=0 cases in both D.C. prime and non-overlapping prime situations.

It will be appreciated from the foregoing that different numbers of turns to those shown may be employed with similar results. It will also be appreciated that in certain circuit applications it is important to have an N I substantially greater than in other applications. In such case, the use of the ratio N =6, N =3, N =3 is preferred. In other circuit applications due to wiring economy, it is important to have the turns N N and N equal. FIGURES 4 and 5 indicate that this is possible.

The circuit of FIGURE 1 shows the use of lumped wiring wherein the advance and prime windings have their multiple turns N particular to each core. It is contemplated that linear wiring circuits may be utilized to achieve further labor savings. The provision of N =N facilitates this since the same physical winding may be made to link the O and E cores in common to accomplish the N and the N functions. Further savings may be made by having N N and N equal and commoned on the cores of the magnetic device.

Changes in construction will occur to those skilled in the art and various apparently different modifications and embodiments may be made without departing from the scope of the invention. The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only. The actual scope of the invention is intended to be defined in the following claims when viewed in their proper perspective against the prior art.

I claim:

1. An improved magnetic core device of the type utilized to transfer intelligence in binary form comprising first, second, and third magnetic cores each having a major and a minor aperture, an advance winding threading said first and third cores in a sense to drive said cores into a clear state of magnetization responsive to an advance pulse applied thereto, an advance winding threading the second of said cores in a sense to drive said second core into a clear state of magnetization responsive to an advance pulse applied thereto, a prime winding threading the minor aperture of each of said cores and adapted to drive each core from a set state of magnetization to a primed set state by reversal of flux orientation in the outer leg adjacent the minor aperture of the core response to prime current applied thereto, a coupling loop linking the outer leg adjacent the transmitting aperture of the first core to the inner leg of the minor aperture of the second core, a coupling loop linking the outer leg adjacent the minor aperture of the second core to the inner leg adjacent the minor aperture of the third core, each coupling loop being adapted to transfer the intelligence state of a preceding core to a succeeding core responsive to the preceding core being driven into a clear state from a primed set state, a hold winding including hold turns linking the outer leg adjacent the lIIllIlOl' aperture of the second core and connected to the advance winding linking the first and third cores, a hold winding including hold turns linking the outer leg of the minor apertures of the first and third cores and connected to the advance circuit linking the second core, the hold turns linking the outer legs of said cores in a sense to apply an MMF opposing the MMF caused by backward transfer current developed in coupling loops linking preceding cores responsive to a succeeding core being driven to the clear state from the primed set state to transfer intelligence to a further succeeding core.

2. The device of claim 1, wherein the advance windings include other turns linking the minor apertures of said cores in a sense to clear the outer legs adjacent said minor aperture responsive to advance pulses.

3. The device of claim 1, wherein the prime winding is supplied by a DC. current.

4. The device of claim 1, wherein the prime winding is supplied by prime pulses partially coincident with advance pulses.

5. The device of claim 1, wherein the prime winding is supplied by pulses non-coincident with advance pulses.

6. In a magnetic core device of the type utilizing a plurality of cores, each having a major aperture and a minor aperture, the circuit improvement comprising means linking said cores with suitable current sources to apply phased distinct magnetomotive forces to drive said cores into distinct stable states of magnetization including clear and prime set states through drive windings including respectively for said states turns N linking core major apertures and N linking core minor transmitting apertures, N linking core minor apertures and N linking core major apertures, further means linking the source of current for N and N turns with holding turns N threading the transmitting minor apertures in the same relative sense as turns N turns N linking the outer leg of magnetic material adjacent the minor transmitting aperture of one core to turns N linking the inner leg of magnetic material adjacent the minor aperture of a succeeding core such as to drive such core into a set state of magnetization responsive to the one core being driven to the clear state from prime set state, the turns N being related to the turns N and N to produce an MMF of a quantity suflicient to counteract the effects developed in a coupling loop connecting a preceding core to the one core as the one core is driven from the prime set state to the clear state to transfer to the succeeding core without having an efiect to disturb the magnetic material about the major aperture of the preceding core.

7. The device of claim 6, wherein N is approximately twice N and N, is less than N 8. The device of claim 6-, wherein N is approximately twice N and N is equal to N 9. The device of claim 6, wherein N is equal to N and N is equal to N References Cited UNITED STATES PATENTS 2,993,197 7/1961 Broadbent 340-174 2,995,731 8/1961 Sweeney 340174 3,045,215 7/1962 Gianola 340174 3,178,694 4/1965 Mallinson 340174 3,229,267 1/1966 Engelbart 340174 BERNARD KONICK, Primary Examiner.

M. S. GITTES, Assistant Examiner. 

1. AN IMPROVED MAGNETIC CORE DEVICE OF THE TYPE UTILIZED TO TRANSFER INTELLIGENCE IN BINARY FORM COMPRISING FIRST, SECOND, AND THIRD MAGNETIC CORES EACH HAVING A MAJOR AND A MINOR APERTURE, AN ADVANCE WINDING THREADING SAID FIRST AND THIRD CORES IN A SENSE TO DRIVE SAID CORES INTO A CLEAR STATE OF MAGNETIZATION RESPONSIVE TO AN ADVANCE PULSE APPLIED THERETO, AN ADVANCE WINDING THREADING THE SECOND OF SAID CORES IN A SENSE TO DRIVE SAID SECCOND CORE INTO A CLEAR STATE OF MAGNETIZATION RESPONSIVE TO AN ADVANCE PULSE APPLIED THERETO, A PRIME WINDING THREADING THE MINOR APERTURE OF EACH OF SAID CORES AND ADAPTED TO DRIVE EACH CORE FROM A SET STATE OF MAGNETIZATION TO A PRIMED SET STATE BY REVERSAL OF FLUX ORIENTATION IN THE OUTER LEG ADJACENT THE MINOR APERTURE OF THE CORE RESPONSE TO PRIME CURRENT APPLIED THERETO, A COUPLING LOOP LINKING THE OUTER LEG ADJACENT THE TRANSMITTING APERTURE OF THE FIRST CORE TO THE INNER LEG OF THE MINOR APERTURE OF THE SECOND CORE, A COUPLING LOOP LINKING THE OUTER LEG ADJACENT THE MINOR APERTURE OF THE SECOND CORE TO THE INNER LEG ADJACENT THE MINOR APERTURE OF THE THIRD CORE, EACH COUPLING LOOP BEING ADAPTED TO TRANSFER THE INTELLIGENCE STATE OF A PRECEDING CORE TO A SUCCEEDING CORE RESPONSIVE TO THE PRECEDING CORE BEING DRIVEN INTO A CLEAR STATE FROM A PRIMED SET STATE, A HOLD WINDING INCLUDING HOLD TURNS LINKING THE OUTER LEG ADJACENT THE MINOR APERTURE OF THE SECOND CORE AND CONNECTED TO THE ADVANCE WINDING LINKING THE FIRST AND THIRD CORES, A HOLD WINDING INCLUDING HOLD TURNS LINKING THE OUTER LEG OF THE MINOR APERTURES OF THE FIRST AND THIRD CORES AND CONNECTED TO THE ADVANCE CIRCUIT LINKING THE SECOND CORE, THE HOLD TURNS LINKING THE OUTER LEGS OF SAID CORES IN A SENSE TO APPLY AN MMF OPPOSING THE MMF CAUSED BY BACKWARD TRANSFER CURRENT DEVELOPED IN COUPLING LOOPS LINKING PRECEDING CORES RESPONSIVE TO A SUCCEEDING CORE BEING DRIVEN TO THE CLEAR STATE FROM THE PRIMED SET STATE TO TRANSFER INTELLIGENCE TO A FURTHER SUCCEEDING CORE. 